Inflatable mattress



FIG. 1 shows a perspective view of the present design;

FIG. 2 shows a front elevational view of the present design;

FIG. 3 shows a rear elevational view of the present design;

FIG. 4 shows a left elevational view of the present design;

FIG. 5 shows a right elevational view of the present design;

FIG. 6 shows a top plan view of the present design; and,

FIG. 7 shows a bottom plan view of the present design.

The dotted lines in FIG. 4 represent stitching. 

The ornamental design for an inflatable mattress, as shown and described. 